Method and apparatus for endovascular thermal thrombosis and thermal cancer treatment

ABSTRACT

A trombus is generated in an aneurysm, arteriovenous malformation or fistula by means of a catheter having an insulated heating coil coupled to an insulated delivery wire. In one embodiment, two delivery wires are coupled to heating coils to provide a closed circuit. The heating coils may be in the form of a double helix or a single helix in combination with a straight heating coil. The heating coils may be electrolytically or mechanically detached therefrom. Alternatively, a single insulated heating coil may be attached to a single insulated delivery wire with a uninsulated coil attached to the tip of the insulated heating coil. The electrical circuit is then made through the heating coil and non-insulated electrode coil into the vascular system and to a body electrode. A catheter may also be used for heating blood within the vascular system which is directly flowed into a tumoral mass for the purposes of thermal treatment of cancer.

RELATED APPLICATIONS

The present application is a continuation-in-part application of U.S.patent application Ser. No. 08/311,508 filed Sep. 23, 1994 and entitled"Improvements in an Endovascular Electrolytically Detachable Wire andTip for the Formation of Thrombus in Arteries, Veins, Aneurysms,Vascular Malformations, and Arteriouvenous Fistulas", now U.S. Pat. No.5,540,680, which was a continuation-in-part application of applicationSer. No. 840,211, filed Feb. 24, 1992, and issued as U.S. Pat. No.5,354,295, which in turn was a continuation-in-part application ofapplication Ser. No. 492,717, filed Mar. 13, 1990 and issued as U.S.Pat. No. 5,122,136, all of which are incorporated herein by reference asif set forth in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the field of endovascular devices andmethodologies and in particular to a means for endovascular heating ofblood for purposes of promoting thrombosis in aneurysms, thrombosis inarteriovenous malformations or fistulas, and thermally heating blood ina tumor for consequent destruction of tumoral cells.

2. Description of the Prior Art

Approximately 25,000 intracranial aneurysms rupture every year in NorthAmerica. The primary purpose of treatment for ruptured intracranialaneurysm is to prevent rebleeding. At the present time, three generalmethods of treatment exist, namely an extravascular, endovascular andextra-endovascular approach.

The extravascular approach is comprised of surgery or microsurgery ofthe aneurysm or treatment site for the purpose of preserving the parentartery. This treatment is common with intracranial berry aneurysms. Themethodology comprises the step of clipping the neck of the aneurysm,performing a suture-ligation of the neck, or wrapping the entireaneurysm. Each of these surgical procedures is performed by intrusiveinvasion into the body and performed from outside the aneurysm or targetsite. General anesthesia, craniotomy, brain retraction and arachnoiddissection around the neck of the aneurysm and placement of a clip aretypically required in these surgical procedures. Surgical treatment ofvascular intracranial aneurysm can expect a mortality rate of 4-8% witha morbidity rate of 18-20%. Because of the mortality and morbidity rateexpected, the surgical procedure is often delayed while waiting for thebest surgical time with the result that an additional percentage ofpatients will die from the underlying disease or defect prior tosurgery. For this reason the prior art has sought alternative means oftreatment.

In the endovascular approach, the interior of the aneurysm is enteredthrough the use of a microcatheter. Recently developed microcatheters,such as those shown by Engleson, "Catheter Guidewire", U.S. Pat. No.4,884,579 and as described in Engleson, "Catheter for GuidewireTracking", U.S. Pat. No. 4,739,768 (1988), allow navigation into thecerebral arteries and entry into a cranial aneurysm.

In such procedures a balloon is typically attached to the end of themicrocatheter and it is possible to introduce the balloon into theaneurysm, inflate it, and detach it, leaving it to occlude the sac andneck with preservation of the parent artery. While endovascular balloonembolization of berry aneurysms is an attractive method in situationswhere an extravascular surgical approach is difficult, inflation of aballoon into the aneurysm carries some risk of aneurysm rupture due topossible over-distention of portions of the sac and due to the tractionproduced while detaching the balloon.

While remedial procedures exist for treating a ruptured aneurysm duringclassical extravascular surgery, no satisfactory methodology exists ifthe aneurysm breaks during an endovascular balloon embolization.

Furthermore, an ideal embolizing agent should adapt itself to theirregular shape of the internal walls of the aneurysm. On the contrary,in a balloon embolization the aneurysmal wall must conform to the shapeof the balloon. This may not lead to a satisfactory result and furtherincreases the risk of rupture.

Still further, balloon embolization is not always possible. If thediameter of the deflated balloon is too great to enter the intracerebralarteries, especially in the cases where there is a vasospasm,complications with ruptured intracranial aneurysms may occur. Theprocedure then must be deferred until the spasm is resolved and thisthen incurs a risk of rebleeding.

In the extra-intravascular approach, an aneurysm is surgically exposedor stereotaxically reached with a probe. The wall of the aneurysm isthen perforated from the outside and various techniques are used toocclude the interior in order to prevent it from rebleeding. These priorart techniques include electrothrombosis, isobutyl-cyanoacrylateembolization, hog-hair embolization and ferromagnetic thrombosis.

In the use of electrothrombosis for extra-intravascular treatment thetip of a positively charged electrode is inserted surgically into theinterior of the aneurysm. An application of the positive charge attractswhite blood cells, red blood cells, platelets and fibrinogen which aretypically negatively charged at the normal pH of the blood. The thrombicmass is then formed in the aneurysm about the tip. Thereafter, the tipis removed. See Mullan, "Experiences with Surgical Thrombosis ofIntracranial Berry Aneurysms and Carotid Cavernous Fistulas", J.Neurosurg., Vol. 41, December 1974; Hosobuchi, "ElectrothrombosisCarotid-Cavenous Fistula", J. Neurosurg., Vol. 42, January 1975; Arakiet al., "Electrically Induced Thrombosis for the Treatment ofIntracranial Aneurysms and Angiomas", Excerpta Medica InternationalCongress Series, Amsterdam 1965, Vol. 110, 651-654; Sawyer et al.,"Bio-Electric Phenomena as an Etiological Factor in IntravascularTrombosis", Am. J. Physiol., Vol. 175, 103-107 (1953); J. Piton et al.,"Selective Vascular Thrombosis Induced by a Direct Electrical Current;Animal Experiments", J. Neuroradiology, Vol. 5, pages 139-152 (1978).However, each of these techniques involves some type of intrusiveprocedure to approach the aneurysm from the exterior of the body.

The prior art has also devised the use of a liquid adhesive,isobutyl-cyanoacrylate (IBCA) which polymerizes rapidly on contact withblood to form a firm mass. The liquid adhesive is injected into theaneurysm by puncturing the sac with a small needle. In order to avoidspillage into the parent artery during IBCA injection, blood flowthrough the parent artery must be momentarily reduced or interrupted.Alternatively, an inflated balloon may be placed in the artery at thelevel of the neck of the aneurysm for injection. In addition to therisks caused by temporary blockage of the parent artery, the risks ofseepage of such a polymerizing adhesive into the parent artery exists,if it is not completely blocked with consequent occlusion of the artery.

Still further, the prior art has utilized an air gun to inject hog hairthrough the aneurysm wall to induce internal thrombosis. The success ofthis procedure involves exposing the aneurysm sufficiently to allow airgun injection and has not been convincingly shown as successful forthrombic formations.

Ferromagnetic thrombosis in the prior art in extra-intravasculartreatments comprises the stereotactic placement of a magnetic probeagainst the sac of the aneurysm followed by injection into the aneurysmby an injecting needle of iron microspheres. Aggregation of themicrospheres through the extravascular magnet is followed byinterneuysmatic thrombus. This treatment has not been entirelysuccessful because of the risk of fragmentation of the metallic thrombuswhen the extravascular magnet is removed. Suspension of the iron powderin methyl methylmethacrylate has been used to prevent fragmentation. Thetreatment has not been favored, because of the need to puncture theaneurysm, the risk of occlusion of the parent artery, the use of unusualand expensive equipment, the need for a craniectomy and generalanesthesia, and the necessity to penetrate cerebral tissue to reach theaneurysm.

Endovascular coagulation of blood is also well known in the art and adevice using laser optically generated heat is shown by O'Reilly,"Optical Fiber with Attachable Metallic Tip for Intravascular LaserCoagulation of Arteries, Veins, Aneurysms, Vascular Malformation andArteriovenous Fistulas", U.S. Pat. No. 4,735,201 (1988). See also,O'Reilly et al., "Laser Induced Thermal Occlusion of Berry Aneurysms:Initial Experimental Results", Radiology, Vol. 171, No. 2, pages 471-74(1989). O'Reilly places a tip into an aneurysm by means of anendovascular microcatheter. The tip is adhesively bonded to a opticfiber disposed through the microcatheter. Optical energy is transmittedalong the optic fiber from a remote laser at the proximal end of themicrocatheter. The optical energy heats the tip to cauterize the tissuesurrounding the neck of the aneurysm or other vascular opening to beoccluded. The catheter is provided with a balloon located on or adjacentto its distal end to cut off blood flow to the site to be cauterized andoccluded. Normally, the blood flow would carry away the heat at thecatheter tip, thereby preventing cauterization. The heat in the tip alsoserves to melt the adhesive used to secure the tip to the distal end ofthe optical fiber. If all goes well, the tip can be separated from theoptical fiber and left in place in the neck of the aneurysm, providedthat the cauterization is complete at the same time as the hot meltadhesive melts.

A thrombus is not formed from the heated tip. Instead, blood tissuesurrounding the tip is coagulated. Coagulation is a denaturation ofprotein to form a connective-like tissue similar to that which occurswhen the albumen of an egg is heated and coagulates from a clear runningliquid to an opaque white solid. The tissue characteristics andcomposition of the coagulated tissue is therefore substantially distinctfrom the thrombosis which is formed by the thrombotic aggregation ofwhite and red blood cells, platelets and fibrinogen. The coagulativetissue is substantially softer than a thrombic mass and can thereforemore easily be dislodged.

O'Reilly's device depends at least in part upon the successfulcauterization timed to occur no later than the detachment of the heattip from the optic fiber. The heated tip must also be proportionallysized to the neck of the aneurysm in order to effectively coagulate thetissue surrounding it to form a blockage at the neck. It is believedthat the tissue in the interior of the aneurysm remains substantiallyuncoagulated. In addition, the hot melt adhesive attaching the tip tothe optic fiber melts and is dispersed into the adjacent blood tissuewhere it resolidifies to form free particles within the intracranialblood stream with much the same disadvantages which result fromfragmentation of a ferromagnetic electrothrombosis.

Therefore, what is needed is an apparatus and methodology which avoidseach of the shortcomings and limitations of the prior art discussedabove.

BRIEF SUMMARY OF THE INVENTION

The invention is an improvement in a catheter for use within a vascularsystem. The improvement comprises at least one delivery wire. At leastone heating coil is coupled to the delivery wire. The delivery wire andheating coil are both electrically insulated to permit endovasculardisposition of the delivery wire and heating coil into the vascularsystem for the purpose of delivering heat to a fluid within the vascularsystem at a predetermined location. Substantially all of the heat isgenerated by electrical current flowing within the heating coil ratherthan within the delivery wire, because of the greater electricalresistance of the heating coil. As a result, endovascular thermaltreatment is provided within the vascular system.

The delivery wire and heating coil are temporarily coupled to each otherand can be selectively detached. In the preferred embodiment thedelivery wire and heating coil are electrolytically detachable from eachother. However, the delivery wire and heating coil may also bemechanically detachable from each other.

The improvement further comprises at least two delivery wires and atleast two heating coils, each having a proximal and distal end. Theproximal end of each of the heating coils is coupled to correspondingones of the two delivery wires. The distal end of the two heating coilsis coupled together to provide a continuous circuit through a first oneof the two delivery wires to a first one of the two heating coils, to asecond one of the two heating coils, and to a second one of the twodelivery wires.

In the illustrated embodiment the two heating coils are each helical andtogether form a double helical tip. In another embodiment one of the twodelivery wires is helical and the other one of the two delivery wires isnonhelical.

In another embodiment the improvement further comprises a body electrodein electrical circuit with the vascular system. The heating coil has aproximal and distal end. The proximal end is coupled to the deliverywire and further comprises an uninsulated coil coupled to the distal endof the heating coil. The electrical resistance of the uninsulated coilis less than the heating coil so that substantially all of the heatgenerated by the current is generated within the insulated heating coil.The uninsulated coil serves as an endovascular electrode to providecompletion of circuit through the delivery wire, and heating coil to thebody electrode.

The improvement further comprises a current source coupled to thedelivery wire for controllably delivering the electrical currentthereto.

The invention is further defined as a method for forming coagulation ofblood at a predetermined location within a vascular system. The methodcomprises the steps of disposing a microcatheter within the vascularsystem at the predetermined location and disposing from themicrocatheter at the predetermined location at least one insulatedheating coil. The insulated heating coil is electrically coupled to aninsulated delivery wire included within the microcatheter and extendsexteriorly to the vascular system. An electrical current delivery wireto the delivery wire to the heating coil to heat fluid within thevascular system at the predetermined location to thermally form athrombus thereat. * As a result, thermal formation of a thrombus withinthe vascular system is selectively formed.

In the illustrated method at least two insulated heating coils connectedtogether in an electrical circuit are disposed in the vascular system.Application of the current to the delivery wire and heating coilresistively generates substantially only within the heating coil.

In one embodiment the method further comprises applying current throughthe insulated heating coil to an uninsulated coil tip in electricalcontact with the fluid in the vascular system to complete an electricalcircuit through the delivery wire, heating coil and coil tip electrodeto a body electrode in electrical communication with the vascularsystem.

The invention is still further characterized as a method for treatingcancer comprising the steps of disposing a microcatheter within thevascular system at the predetermined location in a blood flow to atumoral mass. At least one insulated heating coil is disposed from at bythe microcatheter at the predetermined location. The insulated heatingcoil is electrically coupled to an insulated delivery wire includedwithin the microcatheter and extends exteriorly to the vascular system.An electrical current is applied through the delivery wire to theheating coil to heat the blood flow within the vascular system at thepredetermined location to thermally stress the tumoral mass downstream.As a result, thermal treatment of the tumoral mass is effected.

The invention and its various embodiments may be better visualized byturning to the following drawings wherein like elements are referencedby like numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagrammatic side view of a catheter tipembodying the present invention.

FIG. 2 is a simplified diagrammatic side view of a second embodiment ofthe invention.

FIG. 3 is a simplified diagrammatic side view of a third embodiment ofthe invention.

FIG. 4 is a simplified view of a fourth embodiment of the invention.

FIG. 5 is an idealized diagram showing the placement of a catheterutilizing on of the embodiments of the invention within a vascularaneurysm.

FIG. 6 is a diagrammatic view of another embodiment of the inventionshowing utilization for cancer treatment.

FIG. 7a is a simplified cross sectional side view of an embodiment foruse in a second technique in which the invention may be practiced.

FIG. 7b is a simplified side view of a catheter tip illustrated in asecond embodiment also used in the second technique of the invention.

FIG. 8 is a simplified diagrammatic view which shows a source having aDC generator and an AC or RF generator coupled through a single pole,double throw switch to the delivery wire.

The invention and its various embodiments may now be understood byturning to the following detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A clot is generated in an aneurysm, arteriovenous malformation orfistula by means of a catheter having an insulated heating coil coupledto an insulated delivery wire. In one embodiment, two delivery wires arecoupled to heating coils to provide a closed circuit. The heating coilsmay be in the form of a double helix or a single helix in combinationwith a straight heating coil. The heating coils may be permanentlyconnected to the delivery wires or may be electrolytically ormechanically detached therefrom.

Alternatively, a single insulated heating coil may be attached to asingle insulated delivery wire with an uninsulated coil attached to thetip of the insulated heating coil. The electrical circuit is then madethrough the heating coil and non-insulated electrode coil into thevascular system and to a body electrode.

A catheter may also be used for heating blood within the vascular systemwhich is directly flowed into a tumoral mass for the purposes of thermaltreatment of cancer.

There are two main ways in which the goal of thermal thrombosis can beachieved in the invention, the first of which is illustrated inconnection with FIGS. 1-6, which use some form of a double wire orclosed circuit loop, and the second of which is illustrated inconnection with the catheter tips shown in FIGS. 7a and 7bwhich usessome form of a single wire or body circuit loop.

Within each of these techniques, the invention may be practiced using aplurality of different embodiments or modifications. Further, thecatheter tips of the methodology of the invention can be further be usednot only for the promotion of clotting in aneurysms, arteriovenousmalformations of fistulas, but also in therapeutic treatment of tumoralcells.

Consider first the first technique of endovascular promotion of theformation of clots as illustrated in FIGS. 1-5. As shown in FIG. 1, acatheter, generally denoted by reference numeral 10, is provided withtwo insulated stainless steel delivery wires 12 and 14 covered byinsulating jackets 16. Additional catheter elements as are now known orlater developed in the art may be included in the actual structure ofthe catheter, which is used. Delivery wires 12 and 14 are shown inisolation of the catheter assembly per se inasmuch as the remainingcatheter structure is conventional and largely immaterial to theoperation of the invention. However, it must be clearly understood thatthe delivery wires 12 and 14 are not necessarily disposed in thevascular system as a pair of associated wires as the simplifieddiagrammatic side views of FIGS. 1-4 might suggest. Instead, wires 12and 14 would be appropriately included within a delivery or guidecatheter of conventional design, which is symbolically denoted in FIG. 5by reference numeral 22. Wires 12 and 14 could be coaxial.

Delivery wire 12 terminates at an end 18 of its insulating jacket 16 andis coupled at or near end 18 to a Teflon insulated platinum helix 20.The diameter of platinum helix 20 is typically in the range of 0.1 to0.5 millimeters and may be comprised of a tight helical platinum wire,which when extended from the end of delivery catheter 22 as shown inFIG. 5, forms itself into a helical envelope as depicted by the largehelical form in FIGS. 1-4.

Similarly, stainless steel delivery wire 14 terminates at its end 24 byconnection to a Teflon insulated platinum helical coil 26 which, whenreleased, also extends in the embodiment of FIG. 1 as a helix. Coils 20and 26 thus form a pair of helical coils similar in gross geometry tothe double helical coil of a DNA molecule. Helical coils 20 and 26 arecoupled together at their distal ends 30, or may be fabricated from asingle integral strand of coil, which is then bent or turned at end 30.

The connection between delivery wires 12 and 14 and helical coils 20 and26, respectively, in the embodiment of FIG. 1 is by means of a permanentsolder joint, although other types of mechanical and electricalconnections are contemplated, some of which are described in theembodiments of FIGS. 2-4.

Further, in addition to generally forming a helical envelope as shown inFIG. 1, platinum coils 20 and 26 may be entirely or substantially limp,or without defined or prebiased form, so that a loose bird nest'sconfiguration is formed by the released coils 20 and 26 as opposed tothe tendency to form DNA-like double helix coil structures as shown inthe embodiment of FIG. 1. In other words, coils 20 and 26 may or may notretain some type of geometric association with each other after beingdisposed out of the end of catheter 22 depending on the embodimentutilized.

The electrical resistance of platinum or the platinum tungsten alloyfrom which coils 20 and 26 are fabricated is typically much higher thanthat of the stainless steel delivery wires which comprise wires 12 and14. possible to apply an electrical current to the double helical tip28, which is comprised of coils 20 and 26, to selectively cause tip 28to thermally heat with substantially no heat produced in delivery wires12 and 14, because of the large disparity in the resistance between thetwo.

The electrical current applied to coil tip 28 through delivery wires 12and 14 may be a DC current, alternating current, a radiofrequency powersignal or any combination of the same. Regardless of the frequency ofthe electrical current, the current signal may have any envelope desiredor be modulated in any way desired including modulation in the form ofsine waves, square waves, triangular waves, pulsed, continuous or thelike.

Coils 20 and 26 are Teflon coated or provided with another biologicallynontoxic insulating material to prevent electrical shorting betweencoils 20 and 26 at any point. The solder connections in the embodimentof FIG. 1 between delivery wires 12 and 14 and coils 20 and 26,respectively, may similarly be insulated or placed at differentlongitudinal positions with respect to ends 18 and 24 of insulation 16in order to avoid or to assist in avoiding short circuits between thesolder connections.

The embodiment of FIG. 2 illustrates catheter 10 again in simplifiedside view and is identical in all respects to the embodiment of FIG. 1with the exception that coil 26 has been replaced by a Teflon coatedstraight platinum wire 32. Although wire 32 is shown in FIG. 2 asstraight, it must be understood that wire 32 typically has a diameter of0.025 to 0.25 millimeters and can, in fact, be quite flexible and limp.On the other hand, the stiffness of wire 32 both by its solid geometriccross section, as well as by choice of the platinum-tungsten alloy, canbe chosen to have a variety of different stiffnesses as may be desiredin order to provide a degree of steerability of tip 28, controlledflexibility or malleability for disposition into the target body cavity.

A third embodiment of catheter 10 is illustrated in the simplified sideview of FIG. 3. Again, catheter 10 of FIG. 3 is identical in allrespects to the embodiment of FIG. 1 with the exception that coils 20and 26 are connected to delivery wires 12 and 14 by means ofcorresponding temporary or detachable junctions 34. Tip 28 is preferablyelectrolytically detachable by applying a DC current between deliverywires 12 and 14 and a ground electrode 54, typically applied to anexterior body site and catheter 10 is disposed within the vascularsystem of a patient as shown in FIG. 5. The detailed nature of theelectrolytic detachment of tip 28 as shown in FIG. 3 is described ingreater detail in Guglielmi et al., "Endovascular ElectrolyticallyDetachable Guidewire Tip for the Electroformation of Thrombus inArteries, Veins, Aneurysms, Vascular Malformations and ArteriovenousFistulas," U.S. Pat. No. 5,122,136 (1992), incorporated herein byreference. Alternative means of both electrical and mechanicaldetachment are contemplated within the invention and are furtherdescribed in U.S. Pat. No. 5,122,136 (1992) and U.S. Pat. No. 5,354,295(1994) each of which are similarly incorporated by reference.

Tip 28 is separated from wires 12 and 14 by electrolytic dissolution ofjunctions 34. Junctions 34, which are offset from each other to avoidcontact with each other, are uninsulated and thus exposed to the bloodstream so that they may be electrolytically corroded away at the definedlocation of the junction and coils 20 and 26 separated from deliverywires 12 and 14. Delivery wires 12 and 14 are thereafter removed,leaving tip 28 embedded in the thrombus thermally formed within thevascular cavity.

Another embodiment is depicted in the side view of FIG. 4. Catheter 10of the embodiment of FIG. 4 is substantially identical to the embodimentof FIG. 2 with the exception that coils 20 and 32 are coupled todelivery wires 12 and 14, respectively, through temporary junctions 34of the type described in connection with the embodiment of FIG. 3.

The embodiments of FIGS. 1-4 are employed in the vascular system of apatient as diagrammatically depicted in FIG. 5. The proximal end ofdelivery wires 12 and 14 are coupled to a signal or power source,generally denoted by reference numeral 36. In the illustrated embodimentof FIG. 5, source 36 is diagrammatically shown as symbolically includingthe double pole, double throw switch 38 for selectively coupling eithera DC generator 40 or an AC or RF generator 42 to delivery wires 12 and14. Switch 38 may be of any form, including a solid state switch. Source36 is a conventional power source and may provide a current for theelectrolytic detachment, electrolytic formation of thrombus, and/orthermal formation of thrombi utilizing conventional circuitry or suchcircuits later devised. As a consequence, further details concerningsource 36 will not be discussed.

Catheter 10 is endovascularly disposed within the patient's vascularsystem using conventional medical techniques. Tip 28 is disposed in avascular aneurysm, arteriovenous malformation or fistula, symbolicallydenoted by reference numeral 44, and illustrated in the embodiment ofFIG. 5 as a wide-necked aneurysm 44 having an aneurysm opening or neckapproximately 4 millimeters or greater. The apparatus and methodology ofthe invention is useful without limitation in aneurysms, malformationsand fistulas without limitation, but is shown in connection with awide-necked aneurysm 44 as being used to particular advantage.

Catheter 10 is disposed through vessel 48 into neck 46 to form ahairball or bird nest of coils comprising tip 28. Tip 28 issubstantially proportionally longer then what is suggested in thesimplified depictions of FIGS. 1-4, which, for the sake of simplicity,show tip 28 in a shortened form or at least in a much enlarged scalecompared to that of FIG. 5. Typically tip 28 is 40 mm to 300 long whiledelivery wires 12 and 14 with microcatheter 22 may be 1000 to 1500 mmlong. Coil tip 28 is thus delivered into aneurysm 44 by use ofmicrocatheter 22 which is then withdrawn from aneurysm 44 into frontvessel 48 providing the configuration as illustrated in FIG. 5.Therefore, a portion of delivery wires 12 and 14 are disposed in frontvessel 48 such that in the embodiment of FIGS. 3 and 4, junctions 34 aredisposed in or near aneurysm 44 or its neck 46. Junction 34 is easilydetected through fluoroscopy techniques due to the greater radio-opacityof platinum as opposed to stainless steel.

A second microcatheter 50 is then disposed into vessel 48 which carriesa detachable balloon 52. Balloon 52 is positioned next to neck 46 ofaneurysm 48 and temporarily inflated in front vessel 48 to substantiallyseal across aneurysm neck 46 as depicted in the configuration of FIG. 5or at least to substantial reduce or stop the blood flow past neck 46.Balloon 52 halts the flow of blood allowing the heat that is generatedwithin aneurysm 44, when coil tip 28 is electrically heated, to betrapped within aneurysm 44. In many, if not most, instances, if no bloodflow arrest were provided in vessel 48, the heat would be carried awayby the blood flow and the formation of the thrombus substantiallyimpeded. However, this is not always the case, and in some applicationsthe use of balloon 52 is unnecessary. It is anticipated that in otherapplications, such as narrow necked aneurysms or appropriately shapedvasculated fistulas or malformations, the use of balloon 52 may not benecessary.

An alternating electric current, typically in the range of 20 -40 voltsat 40 -60milliamps, is then applied to the proximal ends of deliverywires 12 and 14 through switch 38 from source 36. Platinum tip 28disposed within aneurysm 44 becomes heated and in turn heats the bloodwithin aneurysm 44 to achieve an intra-aneurysmal thrombosis. Variousways of monitoring the intra-aneurysmal temperature can be utilized andincorporated into the design of coil tip 28. For example, the resistanceof the platinum tungsten alloy is a function of its temperature whichmay be monitored by appropriate conventional resistance detector withinsource 36. Thermal energy dosages can be determined by temperature andtime measurements.

Once thrombosis has been achieved, delivery wires 12 and 14 are thencoupled by means of switch 38 to DC generator 40. Typically, directcurrent of 1 milliamp at 2.5 volts is then applied from DC generator 40through delivery wires 12 and 14 in parallel, utilizing a body electrode54 as the opposite DC electrode. Junctions 34 thus becomeelectrolytically dissolved so that the platinum tungsten tip 28 nowembedded in the clotted aneurysm is detached from catheter 10. Catheter10 and delivery wires 12 and 14 are then pulled away with balloon 52deflated and similarly removed.

While the embodiments of FIGS. 3 and 4 are described as being used in amethod for thrombus formation in FIG. 5, any of the embodiments of theinvention and, in particular the embodiments of FIGS. 1 and 2, may beutilized in applications where endovascular blood heating is needed.FIG. 6 illustrates one such application used for therapeutic treatmentof tumoral cells. In the embodiment of FIG. 6, coil tip 28 of catheter10 is endovascularly disposed within a vessel 56 which leads, forexample, into a vasculated tumoral mass 58. Blood flows in vessel 56 inthe direction indicated by arrow 60. AC or RF current is then applied totip 10 providing a controlled degree of heating of blood 60 such thatthe heated blood is then delivered to tumoral mass 58. Typically, theblood delivered to mass 58 may only be heated by 42 to 47 degreescentigrade to have therapeutic effect. The temperature elevation issufficient for many types of cancers to destroy the tumoral cells. It isfurther expressly contemplated that the tumoral cells may be tagged ortreated to specifically absorb a thermally activated agent that willassist in the destruction of the cell, such as by a thermal cyaninacting in a manner similar to photocyanins. Further, synergistictreatment of tumoral mass 58 is contemplated by combining thermaltreatment as described in FIG. 6 with simultaneous or sequentialchemotherapy or radiation.

FIGS. 7a and b illustrate additional embodiments of catheter 10 utilizedin the second technique of the invention. In the embodiment of FIG. 7a,a single helical platinum-tungsten coil 62 having a Teflon or otherinsulating coating thereon is temporarily coupled by means of adetachable junction 64 to a single stainless steel delivery wire 66,which is disposed within an insulated jacket 68. Again, insulated wire66 may be disposed within a delivery microcatheter or other catheterassembly as is conventionally used. The distal end 70 of the insulatedplatinum-tungsten coil 62 is permanently connected, such as bysoldering, to an uninsulated platinum-iridium coil 72. Coil 72 istypically shorter in length than coil 62. Coil 72 serves as an electrodefor contact with the blood or body tissue for completion of the circuitto a body electrode 54. Platinum-tungsten coil 62 typically has asubstantially higher electrical resistance than either platinum iridiumcoil 72 or stainless steel wire 66, so that substantially all theheating is in coil 62.

The embodiment of FIG. 7b is identical to that described in connectionwith FIG. 7a with the exception that temporary detachable junction 64 isreplaced by permanent or soldered junction 74.

Catheters 10 of FIGS. 7a and 7b are employed in a manner as illustratedin connection with FIG. 8. FIG. 8 is a simplified diagrammatic viewwhich again shows a source 36 having a DC generator 40 and an AC or RFgenerator 42 coupled through a single pole, double throw switch 76 todelivery wire 66. In the embodiment of FIG. 8, AC or RF generator 42 hasits opposing electrode coupled to body electrode 54.

Coil tip 28 is comprised in the embodiments of FIGS. 7a and 7b of coiltip portions 62 and 72 and is disposed by means of microcatheter 22 intovessel 78 and then coupled by means of switch 76 to generator 42. Thecurrent is then applied to delivery wire 66 and current flows to coiltip 28 and thence to uninsulated platinum iridium coil 72, which is theonly portion of tip 28 in electrical contact with the blood or bodyfluids. The only portion of current tip 28 which heats to anysubstantial extent is the platinum tungsten portion, coil 62, because ofits relative high electrical resistance.

If catheter 10 is used to occlude an aneurysm, then coil 62 and 72 oftip 28 are then both exposed within the aneurysm and electrolyticallydetached utilizing the embodiment of FIG. 7a. However, if catheter 10 isused to heat the blood, such as for tumoral treatment as shown in FIG.6, then the embodiment of FIG. 7b is preferably used.

Many alterations and modifications may be made by those having ordinaryskill in the art without departing from the spirit and scope of theinvention. Therefore, it must be understood that the illustratedembodiment has been set forth only for the purposes of example and thatit should not be taken as limiting the invention as defined by thefollowing claims.

The words used in this specification to describe the invention and itsvarious embodiments are to be understood not only in the sense of theircommonly defined meanings, but to include by special definition in thisspecification structure, material or acts beyond the scope of thecommonly defined meanings. Thus if an element can be understood in thecontext of this specification as including more than one meaning, thenits use in a claim must be understood as being generic to all possiblemeanings supported by the specification and by the word itself.

The definitions of the words or elements of the following claims are,therefore, defined in this specification to include not only thecombination of elements which are literally set forth, but allequivalent structure, material or acts for performing substantially thesame function in substantially the same way to obtain substantially thesame result.

In addition to the equivalents of the claimed elements, obvioussubstitutions now or later known to one with ordinary skill in the artare defined to be within the scope of the defined elements.

The claims are thus to be understood to include what is specificallyillustrated and described above, what is conceptionally equivalent, whatcan be obviously substituted and also what essentially incorporates theessential idea of the invention.

We claim:
 1. An endovascular device for use within a vascular systemcomprising:at least one delivery wire having a first resistance; and atleast one detachable heating coil having a second resistance coupled tosaid delivery wire, said first resistance being less than said secondresistance, wherein said delivery wire and heating coil are bothelectrically insulated to permit endovascular disposition of saiddelivery wire and heating coil into said vascular system for the purposeof delivering heat to a fluid within said vascular system at apredetermined location, substantially all of said heat being generatedby electrical current flowing flowing within said heating coil ratherthan within said delivery wire, whereby endovascular thermal treatmentis provided within said vascular system.
 2. The endovascular device ofclaim 1 wherein said delivery wire and heating coil are temporarilycoupled to each other and can be selectively detached while disposed insaid vascular system.
 3. The endovascular device of claim 2 wherein saiddelivery wire and heating coil are electrolytically detachable from eachother.
 4. The endovascular device of claim 2 wherein said delivery wireand heating coil are mechanically detachable from each other.
 5. Theendovascular device of claim 1 further comprising at least two deliverywires and at least two heating coils each having a proximal and distalend, said proximal end of each of said heating coils being coupled tocorresponding ones of said two delivery wires, said distal end of saidtwo heating coils being coupled together to provide a continuous circuitthrough a first one of said two delivery wires to a first one of saidtwo heating coils, to a second one of said two heating coils, and to asecond one of said two delivery wires.
 6. The endovascular device ofclaim 5 wherein said two heating coils are each helical and togetherform a double helical tip.
 7. The endovascular device of claim 6 whereinsaid two delivery wires and two heating coils are temporarily coupled toeach other, each one of said two delivery wires being coupled to one ofsaid two heating coils, and wherein said temporarily coupled deliverywire and heating coil can be selectively detached from each other whilewithin said vascular system.
 8. The endovascular device of claim 6 whereeach one of said two delivery wires are coupled to one of said twoheating coils, wherein each one of said two delivery wires and said twoheating coils are electrolytically detachable from each other.
 9. Theendovascular device of claim 5 wherein one of said two delivery wires ishelical and the other one of said two delivery wires is nonhelical. 10.The endovascular device of claim 7 where each one of said two deliverywires are coupled to one of said two heating coils, wherein each one ofsaid two delivery wires and said two heating coils are temporarilycoupled to each other and can be selectively detached from each other.11. The endovascular device of claim 9 where each one of said twodelivery wires are coupled to one of said two heating coils, and whereineach one of said two delivery wires and said two heating coil areelectrolytically detachable from each other.
 12. The endovascular deviceof claim 1 further comprising a body electrode adapted to be inelectrical circuit with said vascular system and with said deliverywire, wherein said heating coil has a proximal and distal end, saidproximal end being coupled to said delivery wire and further comprisinga uninsulated coil coupled to said distal end of said heating coil, saiduninsulated coil having an electrical resistance, said electricalresistance of said uninsulated coil being less than said heating coil sothat substantially all of said heat generated by said current isgenerated within said heating coil, said uninsulated coil serving as anendovascular electrode to provide completion of circuit through saiddelivery wire and heating coil.
 13. The endovascular device of claim 12wherein said delivery wire and heating coil are temporarily coupled toeach other and can be selectively detached within said vascular system.14. The endovascular device of claim 12 wherein said delivery wire andheating coil are electrolytically detachable from each other.
 15. Theendovascular device of claim 1 further comprising a current source tosaid delivery wire for controllably delivering said electrical currentthereto.
 16. A method for forming a thrombus at a predetermined locationwithin a vascular system comprising:disposing a microcatheter withinsaid vascular system at said predetermined location; disposing from saidmicrocatheter at said predetermined location at least one insulatedheating coil, said insulated heating coil being electrically coupled toan insulated delivery wire included within said microcatheter andextending exteriorly to said vascular system; applying electricalcurrent through said delivery wire to said heating coil to heat fluidwithin said vascular system at said predetermined location to thermallyform a thrombus thereat; and detaching said delivery wire from saidheating coil; and withdrawing said microcatheter and delivery wire fromsaid vascular system, whereby thermal formation of a thrombus withinsaid vascular system is selectively formed.
 17. The method of claim 16where disposing a heating coil in said vascular system comprisesdisposing at least two insulated heating coils connected together in anelectrical circuit.
 18. The method of claim 16 where applying saidcurrent to said delivery wire and heating coil resistively generatesheat substantially only within said heating coil.
 19. The method ofclaim 16 where applying current to said delivery wire and heating coilfurther comprises applying current through said heating coil to anuninsulated coil tip electrode in electrical contact with said fluid insaid vascular system to complete an electrical circuit through saiddelivery wire, heating coil and coil tip electrode to a body electrodein electrical communication with said vascular system.